CHAPTER VIII. 



BRIGHTNESS OF THE CORONA. 



r I THE corona of 1898 was evidently an unusually bright one, 

 _A_ and it is fortunate that several attempts were made in 

 different w T ays to determine the amount of light which it gave 

 as a whole. These attempts will no doubt be valuable rather 

 as affording suggestions for fuller experiments on similar lines 

 in future eclipses than from the actual conclusions to be drawn 

 from them, yet they will probably give us a more exact idea of the 

 brightness of the late eclipse than we have of any preceding one. 



PHOTOGRAPHS OF THE LANDSCAPE. 



THE first method consisted of a series of five exposures on the 

 landscape made by Miss Gertrude Bacon with a quarter-plate 

 camera, Lancaster's instantograph, with the lens at the largest 

 stop at //10. The exposures were identical, and were made with 

 a Norden flap-shutter, giving an exposure of one quarter of a 

 second. The exposures were made at intervals of 10 minutes, 

 reckoning from the instant of mid-totality. The first was taken 

 35 minutes before totality, the second 25 minutes, the third 15 

 minutes, the fourth 5 minutes before, and the fifth 5 minutes after 

 totality. The most interesting circumstance about the series 

 lies in the fact that the fifth photograph is immensely brighter 

 than the fourth, and, indeed, approximates to the third. The 

 recovery of light therefore seems to have been much more rapid 

 than the decline. That it appeared to be more rapid as judged 

 by the eye has long been known, but this was supposed to be a 

 mere physiological effect. It was not suspected that it was 

 a true objective phenomenon. 



The plates employed were Ilford ordinary, and were carefully 

 backed. They were developed simultaneously and for the same 

 time. 



From the nature of the photographs it is impossible to repro- 

 duce them here. The first is enormously over-exposed, and all 

 detail is lost in one undistinguishable glare. The second and 

 third are nearly what would be counted a correct exposure, 

 especially the second, the third being somewhat lightly exposed. 

 The fourth shows only the sky, against which the objects in the 

 foreground stand up in silhouette. The fifth is distinctly under- 

 exposed, but, as said before, is very much brighter than No. 4. 



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